                             :length                 [:ft :m]
                             :mass                   [:lb :kg]
                             :power                  [:hp :W]
-                            :proppant-concentration [:lb-per-gal :lb/gal :kg-per-m3]
+                            :proppant-concentration [:lb-per-gal :kg-per-m3]
                             :slurry-rate            [:bpm :m3-per-min]
                             :volume                 [:bbl :m3]
                             :temperature            [:F :C]}]

        measurement (generate-measurement-f unit)]
    [measurement (measurement-as-f measurement (first (remove (partial = unit) units)))]))

(generate-pair #{:hp :W} rand-power-unit typical-power power-as)

   (let [unit (rand-proppant-concentration-unit)]
     (typical-proppant-concentration unit)))
  ([unit]
   (let [typical-value (cond (= unit :lb-per-gal)
                             (value-from-typical-range 0.2 10)
                             (or (= unit :kg-per-m3)
                                 (= unit :kg/m3))
